The main reason commercial airplanes require separation is to avoid collisions. Commercial airliners carry hundreds of passengers and operate under civil air traffic regulations, which are followed by every commercial aircraft flying in that airspace. By maintaining a safe distance, they ensure that they do not cross paths with other aircraft, reducing the risk of collisions.
If the title seems unclear or confusing, let me explain further.
You might already know that commercial planes need to keep a certain distance from other commercial planes during flight. This is why Air Traffic Control (ATC) exists. One of the primary responsibilities of ATC workers is to ensure that every plane taking off, landing, or passing through their airport does not fly too close or interfere with other planes in the same airspace.
The individuals working in ATC have a significant responsibility. The safety of thousands of people depends on how they manage the airspace around their airport. (Photo Credit: Slashme / Wikimedia Commons)
If this separation is not maintained, it could potentially lead to a catastrophic event. That is why commercial airplanes maintain a safe distance from other planes in their vicinity.
However, military aircraft operate differently. They often fly in close formations intentionally. They do not maintain a significant distance from other military aircraft in the formation. This may seem counterintuitive.
Why do large commercial airplanes require vertical and horizontal separation, while military aircraft do not?
Separation
In the field of aviation, the term “separation” refers to the concept of keeping a plane at least a minimum distance from another aircraft. The primary reason for this is to prevent mid-air collisions and avoid accidents caused by factors such as wake turbulence.
In the United States, the Federal Aviation Administration (FAA) defines the standard aircraft separation guidelines under Instrument Flight Rules (IFR). According to these guidelines, two planes must maintain a minimum of 1000 feet (305 meters) of vertical separation or 3 miles of lateral separation. These values increase for larger aircraft.
Interestingly, not all aircraft are required to maintain separation as specified by ATC. Whether separation is necessary depends on the airspace class in which the aircraft is flying and the rules followed by the pilots. There are three sets of rules under which an aircraft can operate: Visual Flight Rules (VFR), Special Visual Flight Rules (SVFR), and Instrument Flight Rules (IFR). Commercial aircraft almost always operate under IFR.
This picture was taken from inside a passenger airliner (Boeing 767) at cruising altitude. Notice the trail of another airplane flying below it. You can see the separation between both these aircraft. (Photo Credit: Downtowngal / Wikimedia Commons)
Why is Separation Necessary for Commercial Planes?
The main reason for separation is to prevent collisions. Commercial planes carry a large number of passengers, unlike military jets, and they operate under civil air traffic guidelines. By maintaining an appropriate clearance, commercial planes ensure that they do not intersect with the paths of other aircraft, reducing the risk of collisions.
An additional reason for separation is wake turbulence. When a large plane flies, its wings generate lift, creating turbulence in its wake.
This image from a NASA study on wingtip vortices visually demonstrates wake turbulence. (Photo Credit: NASA Langley Research Center (NASA-LaRC) / Wikimedia Commons)
If two commercial planes fly too close to each other, they may be affected by the disturbance caused by the leading plane, which can have negative consequences for the trailing plane.
Commercial planes are also less maneuverable than military planes, and their pilots are not typically trained in formation flight. Furthermore, there is no significant reason to reduce the existing separation between planes.
Why Can Military Aircraft Fly in Close Formation?
Military aircraft also require a minimum separation from other aircraft, but they are able to fly in close formations consisting of multiple planes. There are several reasons for this.
Pretty cool, isn’t it? (Photo Credit: Pxhere)
Fighter aircraft are much more maneuverable than commercial planes. They can execute quick turns and steep climbs or descents at a moment’s notice. In addition to avoiding wake turbulence, separation between military aircraft is primarily for safety during sudden and unexpected maneuvers. Military pilots communicate directly with each other on a specific radio frequency and are aware in advance of the maneuvers their fellow pilots will make, allowing them to prepare accordingly.
Prior to the flight, each pilot in the formation is briefed on the flight plan and the specific formations they will fly in. This minimizes the likelihood of an unexpected maneuver. Therefore, military pilots are able to perform daring maneuvers in the air because they are meticulously planned and prepared.
(Photo Credit: U.S. Air Force photo/Tech. Sgt. Justin Pyle)
Lastly, military pilots are extensively trained to fly in tight formations. They spend significant time learning about and practicing flying in such formations. Commercial pilots, on the other hand, generally do not have the same level of training or expertise to fly in close proximity to other commercial planes.
This is why commercial planes need to maintain a safe distance from each other, while military aircraft often fly very close to each other.